Ovarian cancer is the fifth leading cause of cancer-related deaths in women. The majority of patients is diagnosed at late stages of disease due to inadequate detection methods, and is treated with surgery followed by chemotherapy. Due to the advanced stage of disease at diagnosis, there is a high rate of recurrence. The five-year survival rate of ovarian cancer is 20% below the average five-year survival rate for all cancer combined, highlighting the need for innovative therapies for ovarian cancer. Rapid and inexpensive sequencing technology has allowed for the ongoing efforts to profile individual cancer genomes and subsequent identification of new therapeutic candidates. However, the development of small molecule inhibitors against newly identified targets is expensive, slow, and many targets are undruggable. RNAi therapy offers an attractive course of treatment: siRNA against new targets can be rapidly synthesized and can target specific isoforms which may not be possible by small molecule therapy. However, at this stage, efficient delivery of siRNA into the cytosol of diseased cells remains a major challenge. We propose utilizing primary ovarian cancer cells as a clinically relevant model of disease to optimize siRNA delivery vehicles for ovarian cancer therapy. There are several mouse models utilized to develop therapeutics for ovarian cancer, including genetically engineered mouse models and xenografts of ex vivo propagated cell lines. Although useful, these models may not represent the human etiology of high-grade ovarian cancer, the greater majority of which originate from the fallopian tube. Primary ovarian cells isolated from the ascites of human patients may more accurately represent disease development and the heterogeneity of cancer cells, and therefore may be more useful in evaluating the response to therapy. Characterization of primary ovarian cancers may provide insights to develop therapeutics that will be ultimately translated into humans. The purpose of this proposal is the development of siRNA delivery carriers to clinically relevant models of ovarian cancer. We will fine-tune our first generation carrier which includes (1) a peptide for targeting ectopically expressed p32 and (2) a peptide for mediating endosomal escape of internalized siRNA. First, we will characterize primary ovarian cancer cells for surface representation of the cognate receptor of our targeting peptide. Next, targeting peptide will be optimized for internalization and delivery of siRNA in primary ovarian cancer cells in vitro, as well as optimal biodistribution in vivo. These optimized vehicles will then be applied for therapeutic delivery of siRNA in primary ovarian cancer xenograft models. A multi-component peptide siRNA delivery vehicle has broad applicability to other cancer subtypes via interchanging targeting moieties and cargo.